Wang Mengcheng, Liu Chun, Xing Tian, Wang Yanxia, Xia Guangmin
The Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Science, Shandong University, 27 Shandanan Road, Jinan, 250100, Shandong, P. R. China.
Shijiazhuang Academy of Agriculture and Forestry Sciences, 479 Shengli North Avenue, Shijiazhuang, 050041, Hebei, China.
BMC Genomics. 2015 Oct 17;16:807. doi: 10.1186/s12864-015-1974-6.
Allopolyploid genome needs wide structural variation to deal with genomic shock. The introgression line, generated via asymmetric somatic hybridization, is introgressed with a minimum of exogenous chromatin, which also leads to genomic shock to induce genetic variation. However, the extent of its genomic variation and its difference from allopolyploidies remains unknown.
Here, we explored this issue using the bread wheat cultivar SR3, a derivative of an asymmetric somatic hybrid between the cultivar JN177 and an accession of tall wheatgrass (Thinopyrum elongatum). The ESTs (expressed sequence taqs) were large-scale sequenced using the cDNA library constructed in each of SR3 and JN177. Point mutations and indels (insertions and deletions) of SR3 were calculated, and their difference from the genetic variation of bread wheat and its ancestors were compared, with aim to analyze the extent and pattern of sequence variation induced by somatic hybridization.
Both point mutations and indels (insertions and deletions) were frequently induced by somatic hybridization in the coding sequences. While the genomic shock caused by allopolyploidization tends to favor deletion over insertion, there was no evidence for such a preference following asymmetric somatic hybridization. The GC content of sequence adjacent to indel sites was also distinct from what has been observed in allopolyploids.
This study demonstrates that asymmetric somatic hybridization induces high frequency of genetic variation in a manner partially different from allopolipoidization. Asymmetric somatic hybridization provides appropriate material to comprehensively explore the nature of the genetic variation induced by genomic shock.
异源多倍体基因组需要广泛的结构变异来应对基因组冲击。通过不对称体细胞杂交产生的渐渗系，仅渗入了最少的外源染色质，这也会引发基因组冲击以诱导遗传变异。然而，其基因组变异的程度以及与异源多倍体的差异仍不清楚。
在此，我们使用面包小麦品种SR3来探究这个问题，SR3是品种JN177与高冰草（Thinopyrum elongatum）的一个材料之间不对称体细胞杂交的衍生物。利用在SR3和JN177中各自构建的cDNA文库对ESTs（表达序列标签）进行大规模测序。计算SR3的点突变和插入缺失（插入和缺失），并将其与面包小麦及其祖先的遗传变异进行比较，旨在分析体细胞杂交诱导的序列变异的程度和模式。
体细胞杂交在编码序列中频繁诱导点突变和插入缺失。虽然异源多倍体化引起的基因组冲击倾向于缺失而非插入，但没有证据表明不对称体细胞杂交后存在这种偏好。插入缺失位点附近序列的GC含量也与在异源多倍体中观察到的不同。
本研究表明，不对称体细胞杂交以部分不同于异源多倍体化的方式诱导高频遗传变异。不对称体细胞杂交为全面探究基因组冲击诱导的遗传变异的本质提供了合适的材料。
